Definition: Refractory Ventricular Arrhythmias

  • Persistent ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT) despite ≥3 shocks, appropriate CPR, vasopressors, and anti-arrhythmics.

Epidemiology

  • Refractory VF occurs in roughly 10–25% of out-of-hospital cardiac arrest (OHCA) cases.

  • Linked with extremely poor outcomes: survival to discharge ~2–12%.

  • Increasing use of mechanical CPR and ECMO has driven interest in novel defibrillation strategies.

Background: Standard Defibrillation (Based on ACLS Guidelines)

  • Indication:

    • Primary intervention for pulseless VT/VF, the most common initial rhythm in witnessed cardiac arrest.

  • Pad Placement:

    • Standard pad positioning is anterior-lateral (AL):

      • One pad below the right clavicle (sternal region)

      • One pad lateral to the left nipple (apical position)

Figure 1: Cheskes S, Verbeek PR, Drennan IR, et al. Defibrillation strategies for refractory ventricular fibrillation. N Engl J Med. 2022;387(21):1947–1956. doi:​10.1056/NEJMoa2207304

  • Shock Type:

    • Unsynchronized for pulseless VF/VT

    • Synchronized for unstable monomorphic VT with a pulse

  • Energy Recommendations:

    • Biphasic: 120–200 J (varies by device manufacturer)

    • Monophasic: Fixed at 360 J

  • Shock Protocol:

    • Deliver shock immediately after rhythm analysis confirms VF/VT.

    • Resume high-quality CPR immediately post-shock.

    • Administer epinephrine every 3–5 minutes.

    • Introduce antiarrhythmic drugs (e.g., amiodarone, lidocaine) after the third shock.

Alternative Defibrillation Strategies

  • Vector Change (VC) Defibrillation:

    • A single defibrillator is used.

    • Pads repositioned from AL to AP to change the shock vector.

    • Theoretically re-engages different myocardial fibers or improves current delivery.

Figure 1: Cheskes S, Verbeek PR, Drennan IR, et al. Defibrillation strategies for refractory ventricular fibrillation. N Engl J Med. 2022;387(21):1947–1956. doi:​10.1056/NEJMoa2207304

  • Dual Sequential External Defibrillation (DSED):

    • Uses two defibrillators delivering sequential high-energy shocks.

    • Pads placed in both AL and anterior-posterior (AP) positions.

    • Goal: Engage multiple vectors and potentially overcome high defibrillation thresholds.

  • Dual Dose Defibrillation:

    • Two defibrillators deliver simultaneous shocks.

    • Controversial due to concerns of myocardial injury; less commonly practiced.

History of Dual Sequential Defibrillation

  • DSED emerged in case reports from the 1990s; gained popularity through anecdotal success and observational data.

  • First large-scale RCT (DOSE-VF) published in NEJM 2022.

Pathophysiology: How DSED Might Work

  • Power Hypothesis:

    • Two sequential shocks may summate energy, reaching thresholds unreached by single shocks.

  • Priming Theory:

    • First shock may lower myocardial resistance, allowing the second to more effectively depolarize myocardium.

  • Multi-Vector Theory:

    • Dual pad positions apply energy through different planes, increasing the chance of disrupting reentrant circuits in VF.

  • Improved Myocardial Engagement:

    • Engages more myocardial mass and potentially overcomes anisotropy (directional resistance) in damaged cardiac tissue.

Methodology: How to Perform Dual Sequential Defibrillation

  • Team Coordination Is Key:

    • Two defibrillators, two sets of pads, and a coordinated team approach are required.

  • Pad Placement:

    • Defibrillator A (Standard): AL position

    • Defibrillator B (Alternate): AP position (posterior pad placed beneath scapula)

  • It is essential that pads are not touching otherwise you risk damaging both defibrillators.

Figure 1: Cheskes S, Verbeek PR, Drennan IR, et al. Defibrillation strategies for refractory ventricular fibrillation. N Engl J Med. 2022;387(21):1947–1956. doi:​10.1056/NEJMoa2207304

  • Charging & Delivery:

    • Both defibrillators charged to max energy (e.g., 200 J biphasic).

    • Shocks delivered in rapid succession — ideally <1 second apart (simultaneous not required, and may be less effective).

  • Safety Protocols:

    • Clear communication — designate a leader to call “Clear!”

    • Ensure nobody is touching the patient.

    • Verify pad cables are not crossing to avoid arc or equipment failure.

  • When to Use:

    • Consider DSED after three failed standard defibrillation attempts.

    • Most often used during refractory OHCA with ongoing CPR.

Prognosis: Does DSED Improve Outcomes?

Evidence from the DOSE-VF Trial (NEJM 2022)

  • Survival to Hospital Discharge:

    • DSED: 30.4%

    • VC: 21.7%

    • Standard: 13.3%

  • Neurologically Intact Survival:

    • DSED: 27.4%

    • VC: 16.2%

    • Standard: 11.2%

  • VF Termination and ROSC:

    • DSED had higher rates of ROSC (46%) and VF termination (84%) than standard approaches.

Findings from 2024 Resuscitation Journal Secondary Analysis

  • In shock-refractory VF:

    • Survival with DSED: 28.6%

    • Survival with VC: 9.1%

    • Standard defibrillation: 0%

  • In recurrent VF:

    • DSED still showed a survival advantage over VC and standard approaches.

Adjunctive Therapies in Refractory Ventricular Arrhythmias

Medications

  • Esmolol:

    • Ultra-short-acting beta-1 blocker.

    • Used to blunt catecholamine-driven myocardial excitability.

    • Dose: 500 mcg/kg IV bolus → 50–100 mcg/kg/min infusion.

    • Some observational studies suggest improved ROSC and survival.

  • Lidocaine:

    • Alternative to amiodarone.

    • May be preferred in early refractory VF, especially in cases of ischemia or torsades.

    • “A retrospective ‘target trial emulation’ comparing amiodarone and lidocaine for adult out-of-hospital cardiac arrest resuscitation” (March 2025) demonstrated lidocaine administration compared to amiodarone was associated with higher odds of:
        • prehospital return of spontaneous circulation (ROSC) (36.0% vs. 30.4%; adjusted odds ratio [aOR]: 1.29)
        • fewer post-drug defibrillation attempts
        • greater odds of survival to hospital discharge (35.1% vs. 25.7%; OR: 1.54)

  • Magnesium:

    • Consider in torsades de pointes or suspected hypomagnesemia.

Mechanical Support & Other Techniques

  • Mechanical CPR: Allows uninterrupted compressions during defibrillator coordination.

  • ECMO: For patients with persistent VF and good pre-arrest function; enables continued perfusion while managing arrhythmia.

  • PCI: Should be considered early in arrest of suspected ischemic origin.

  • Stellate Ganglion Block (experimental): May blunt sympathetic surge in refractory cases.

Take Aways

  • DSED is not yet standard of care but supported by growing clinical evidence, especially for shock-refractory VF.

  • It shows higher survival and neurologically intact outcomes compared to standard and VC strategies.

  • Implementation requires two defibrillators, team coordination, and protocol familiarity.

  • Should be combined with appropriate pharmacologic and procedural adjuncts for optimal effect.

 

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Episode 190: Electrical Storm

References

  1. Cheskes S, Verbeek PR, Drennan IR, et al. Defibrillation strategies for refractory ventricular fibrillation. N Engl J Med. 2022;387(21):1947–1956. doi:10.1056/NEJMoa2207304

  2. Cheskes S, Drennan IR, Turner L, Pandit SV, Dorian P. The impact of alternate defibrillation strategies on shock-refractory and recurrent ventricular fibrillation: A secondary analysis of the DOSE VF cluster randomized controlled trial. Resuscitation. 2024;198:110186. doi:10.1016/j.resuscitation.2024.110186

  3. Renslow M, Maloney J, Snell A. Dual Sequential Defibrillation (DSD). REBEL EM. Published April 8, 2019. Accessed April 23, 2025. https://rebelem.com/dual-sequential-defibrillation-dsd

  4. Advanced Cardiovascular Life Support. In: StatPearls. Treasure Island, FL: StatPearls Publishing; 2024. https://www.ncbi.nlm.nih.gov/books/NBK544231

  5. Cheskes S, Turner L, Drennan IR, et al. Outcomes of patients with recurrent ventricular fibrillation treated with alternative defibrillation strategies: a DOSE VF sub-analysis. Resuscitation. 2025;191:109910. [ScienceDirect Access via NYU Library]

  6. Panchal AR. Updates in the Management of Refractory Ventricular Tachycardia or Ventricular Fibrillation Arrest. ACEP Now. Published August 9, 2023. Accessed April 23, 2025. https://www.acepnow.com/article/updates-in-the-management-of-refractory-ventricular-tachycardia-or-ventricular-fibrillation-arrest

  7. Smida T, Crowe R, Price BS, et al. A retrospective ‘target trial emulation’ comparing amiodarone and lidocaine for adult out-of-hospital cardiac arrest resuscitation. Resuscitation. 2025;208:110515. doi:​10.1016/j.resuscitation.2025.110515